192 clutches and power-stop control – Clutches – Fluent material
Patent
1988-05-13
1990-05-15
Bonck, Rodney H.
192 clutches and power-stop control
Clutches
Fluent material
192 82T, F16D 3500, F16D 4325
Patent
active
049249860
DESCRIPTION:
BRIEF SUMMARY
This invention relates to rotary clutches or torsional transmission devices of the type having a rotary casing with an internal rotary element between which is provided a small annular clearance gap. When this gap is occupied by viscous fluid torque can be transmitted between the two parts and the amount of torque can be varied by adjusting the amount of fluid in the gap.
It has been proposed to adjust the amount of fluid in the gap by providing an automatic fluid impeller acting between the two parts and arranged to convey the fluid from the outer periphery of the gap inwards to a fluid chamber or reservoir from which the fluid then returns outwards towards the gap. By adjusting the rate of circulation of the fluid the volume in the gap can be adjusted.
Existing designs of this type suffer from various disadvantages. They tend to be slow acting and the need to accommodate considerable volumes of fluid in the reservoir tends to increase the overall dimensions and weight of the clutch. Accordingly it is an object of the invention to provide an improved rotary clutch or transmission device of the kind referred to which will avoid some of the existing difficulties.
Broadly stated the invention consists in a viscous fluid clutch or torsional drive comprising a rotary casing containing an internal rotary element defining an annular clearance gap, a fluid reservoir adjacent the rotary axis having a fluid exit aperture communicating with the clearance gap, and a pump for impelling fluid radially inwards from the outer periphery of the gap into the reservoir.
According to a preferred feature of the invention the unit includes a valve arranged to close or restrict the pressure line from the pump to the reservoir. The valve may act directly to close or restrict the flow line to the reservoir from the pump. Alternatively there may be a servo-operated valve responsive to the increase in pressure when the aforementioned valve is closed. The servo-valve is preferably arranged to open the or an exit from the reservoir.
In any case the valve is preferably arranged to prevent reverse flow through the pump when the pump is inoperative or less effective at low speeds.
According to another preferred feature of the invention there is a permanently open outlet from the reservoir.
In one particularly preferred construction, there are two separate reservoirs each controlled by a respective valve in a pressure line from the pump, and the two reservoirs may be associated respectively with dual control valves controlling the discharge of fluid from the reservoir to the clearance gap. Preferably one of the two valves has a thermal sensing element responsive to ambient air temperature and the other valve has a remote operated coolant temperature sensing system.
The invention may be performed in various ways and a number of embodiments will now be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a half-sectional side elevation through a viscous fluid clutch according to the invention, and
FIGS. 2, 3 and 4 are also sectional half elevations through other embodiments of the invention.
In the embodiment of FIG. 1 the viscous clutch comprises a rotary casing formed by two main shells 10,11 bolted together and providing an internal annular chamber in which is received an inner rotary element 13 which has a plurality of annular ribs 14 on its opposite faces extending into corresponding grooves 15 formed in the two shells 10,11. This arrangement provides a labyrinth annular clearance gap between the casing and the inner member 13 and when occupied by a viscous fluid torsion is transmitted in known manner between the two rotary members. The internal member 13 is secured to a drive flange 18 intended to be bolted to a drive shaft, not shown, and the casing shell 11 has bolt fixings 19 by which it can be secured, for example, to an output shaft or to a cooling fan or other power absorber.
Means are provided for varying the quantity of the viscous fluid present in the annular clearance gap so as to cont
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Bonck Rodney H.
Kysor Industrial Corporation
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